Not Applicable
Not Applicable
Not Applicable
1. Field of the Invention
The invention concerns a filter device for extruders and injection molding machines according to the precharacterizing clause of the main claim.
2. Description of the Related Art
A filter device representing this type is described in DE 42 18 756 C1.
From DE 295 17 140 U1 a filter device has become known in which an oval sieve is inserted into the sieve bolt. With this previously known form of embodiment it is a matter of a sieve exchanger in which the extruder must be turned off during the sieve exchange, so that the seal length between the material duct and the housing outer edge may be smaller than in the case of a continuous sieve exchanger.
The object on which the invention is based is to make available in a filter device of the generic type a large sieve surface that, however, is arranged in a relatively small housing, so that the entire arrangement is not built larger than the filter devices that are usual in the prior art. Achieved through the large sieve surface is a long service life and, furthermore, good filtering results with normal throughput, in comparison to the normal sieves that are usual in the prior art. Thus, an increase in throughput in comparison to normal sieves is aimed at.
This object forming the basis of the invention is accomplished through a filter device for extruders and injection molding machines for processing the plastics, with filter elements exchangeably arranged in at least two separate ducts of a housing between at least one main admission duct and at least one main outlet duct in sieve carrier bolts in sieve openings, which filter elements can be pushed in or pulled out with the sieve carrier bolts arranged in the respective housing bores; in this, in the region of the main admission duct at least one blocking means is arranged in front of the sieve carrier bolts, which blocking means in the flow position does not hinder the stream of plastic moving from the main admission duct to the filter elements, but which in the blocking position separates the flow of the plastic in a partial admission duct from the main admission duct, characterized by the fact that:
a) the filter elements in the sieve carrier bolts are formed as ovals in a manner known per se, the long axis of the oval extending in the direction of the displacement of the sieve carrier bolts and the length of the oval axis of the filter elements with respect to the length of the housing bore in the housing being chosen in such a manner that only the length of the sieve carrier bolts necessary for the sealing of the sieve carrier bolts in the housing bore is free of the filter element,
b) and the partial admission ducts each open into a sieve opening in at least two inflow ducts.
Advantageous developments of the invention include but are not limited to the following.
The filter element may include ventilation grooves formed in the sieve carrier bolts and connected with the sieve openings that accommodate the filter elements.
Provision may be made for at least one outflow duct for each sieve opening.
The blocking means may be formed by a bolt that traverses the main admission duct and is adjustable transversely to the flow direction of the plastic stream to be filtered, and the flow path from the main admission duct to the admission ducts may be formed by a narrow section in the outer periphery of the bolt.
A main discharge duct may be present in the bolt, which duct opens at one end into the atmosphere and to which are connected two partial discharge ducts, which upon displacement of the bolt can be brought into a fluid connection with one or the other partial admission duct In the fluid connection of the partial discharge ducts with the associated partial admission ducts, the flow cross-section in the transition region between the partial admission ducts and the partial discharge ducts may be smaller than the flow cross-section of the partial admission ducts.
The blocking means may be arranged in the housing of the sieve exchanger.
The blocking means may be arranged in its own housing, which is attachable to the housing of tee filter device.
The bolt may be round in shape and the narrow section is designed over the entire circumference of the bolt.
The bolt, on its side facing the main admission duct, may displays a bypass duct that, depending on the position of the bolt, is able to produce a connection between the main admission duct and the outside atmosphere.
The opening of the bypass duct into the main admission duct may be arranged so that the main admission duct can be brought into fluid connection with both the narrow section and the bypass, but that through adjustment of the bolt the connection between the main admission duct and the narrow section is closable while the connection between the main admission duct and the bypass duct is open.
The bolt of the blocking means, in addition to its movement in the longitudinal axis, also may be rotatable around the longitudinal axis.
This object forming the basis of the invention is also accomplished through blocking means for controlling the throughput of a flowable medium, with filter elements arranged in at least two separate ducts of a housing between at least one main admission duct and at least one main outlet duct, the blocking means being arranged in the region of the main admission duct in front of the filter elements;
and in the flow-through position not hindering the flow of the flowable medium from the main admission duct to the filter elements, but in a blocking position separating the flow-through of the medium in an admission duct from the main admission duct, characterized by the fact that the blocking means is formed by a bolt, arranged in a housing, which bolt traverses the main admission duct and is adjustable adversely to the flow direction of the flowable medium, and tat the flow path from the main admission duct to an outlet duct is formed by a narrow section in the outer periphery of the bolt.
Advantageous developments of the invention may also include but are not limited to the following.
The narrow section may be designed so as to allow an efficient flow.
The blocking means may include a main discharge duct in the bolt, which duct on one end opens into the atmosphere and connects to two partial discharge ducts, which upon a displacement of the bolt can be brought into fluid connection with one of the partial admission ducts.
During the fluid connection of the partial discharge ducts with the associated partial admission ducts the flow cross-section in the transition region between the partial admission ducts and the partial discharge ducts may be smaller tan the flow cross-section of the partial admission ducts.
The blocking means may be arranged in its own housing, which is attachable to the housing of the filter device.
The blocking means may be arranged in the housing of the sieve exchanger.
The bolt may be round in shape and the narrow section is designed over the entire circumference of the bolt.
The bolt, on its side facing the main admission duct, may display a bypass duct that, depending on the position of the bolt, is able to produce a connection between the main admission duct and the outside atmosphere.
The opening of the bypass duct into the main admission duct may be arranged so that the main admission duct can be brought into fluid connection with both the narrow section and the bypass, but that through adjustment of the bolt the connection between the main admission duct and the narrow section is closable while the connection between the ma admission duct and the bypass duct is open.
The bolt of the blocking means, in addition to its movement in the longitudinal axis, also may be rotatable around the longitudinal axis.
Expressed in different words, it is proposed that the sieve in each sieve carrier bolt is designed so as to be virtually the size, i.e. the length considered in the displacement direction of the sieve carrier bolt, of the actual housing that accommodates the sieve carrier bolts. In this, there arises the difficulty that during the extracting of the sieve, i.e. of the filter element, the latter already comes into contact with the atmosphere in a peripheral region of the filter element, so that a flowing out of the filtered and to-be-filtered plastic occurs. Thus, it must be ensured that, at the moment when the sieve carrier bolt begins its pulling-out movement, the partial admission duct, assigned to this sieve opening, of the main admission duct is closed off. On the other hand, it must be ensured that during the driving in of the sieve carrier bolt to its filtering position a pre-ventilation of the sieve opening can take place, during which the partial admission duct assigned to the other sieve carrier bolt is still loaded with the plastic material to be filtered. By virtue of this blocking position achievable through the blocking means, the possibility of a large, oval sieve design comes about.
With the use of a large, oval sieve, according to the invention it is proposed that the admission ducts in each case open into two inflow ducts, whereas, however, only one outflow duct can be planned for each sieve opening. In this way, favorable inflow and outflow conditions are produced.
The blocking means is preferable designed as a bolt, and this bolt, preferable arranged in an attachment housing, displays a flow opening for the plasticized plastic material, the flow opening being formed by the bolt""s having a preferably circumferential narrow section, through which can flow the stream of plastic. This narrow section leads into the mouth of the two partial admission ducts. The bolt is displaceable in a direction transverse to the stream of plastic and displays in addition a main discharge duct and partial discharge ducts, which connect to the main discharge duct. Through a displacement of the bolt, a position can now be attained in which the admission duct is connected to the partial admission duct via the narrow section designed in the bolt. By means of the controls standard today, this bolt that forms the locking means can be positioned such that, on the one hand, the partial admission duct leading to the sieve opening is completely closed off, and on the other hand the possibility exists, despite the loading of the other partial admission duct, of creating a connection to the other partial admission duct, so that here a pre-flooding of the sieve opening is made possible.
In addition, the bolt designed according to the dependent claims makes it possible that when the bolt assumes a position in which the main admission duct is connected to the partial admission duct via the narrow section designed in the bolt, the other partial admission duct is connected via a partial discharge duct to the main discharge duct, so that the loading of the mold connected to the filter device still takes place, but at the same time the idle sieve can be run through from the clean side of the sieve towards the dirty side of the sieve and the dirt particles removed here flushed back through the partial admission duct assigned to this sieve and then conducted via a partial discharge duct into the main discharge duct. The main discharge duct here leads to the atmosphere.
The bolt designed as a blocking means displays, on its side facing the main admission duct, a bypass duct, which in dependence on the position of the bolt is capable of producing a connection between the main admission duct and the outside atmosphere.
In addition, the invention relates to a blocking means for controlling the throughput of a flowable medium independently of the subsequently connected unit, for example the above described filter device. The blocking means can also be used in conjunction with other flowable media that are to be controlled.